PRINCIPLE OF OPERATION cont.:
The signal is then led through a double monolitic crystal filter to the
SECOND MIXER, where the signal is mixed with the fL02 signal having con-
tinuous tuning in the frequency range from
10.00795
MHz to
10.00915
MHz
or
16.00795
MHz to
16.00915
MHz, and thus giving a 2nd IF frequency of
600
kHz.
The
16.6085
MHz
1st
IF is selected in the frequency range
0.0100
MHz to
13.9999
MHz and
10.6085
MHz in the range
14.0000
MHz to 29.9999 MHz.
The protluced 2nd IF signal is led through one of the five filters avail-
able on the IF FILTER UNIT. The switching takes place electronically by
means of the MODE and/or the FILTER SWITCH.
The signal is then passed on to the IF2 AMPLIFIER and DETECTOR. The IF
amplifier consists of 3 AGC controlled amplifier stages. The detector for
both AM and SSB reception is an envelope detector, and in the SSB and CW
mode the carrier is reinjected in such a way that the incoming signal is
converted to an A3H signal.
l
The reinjected carrier in SSB mode is 600 kHz
derived
from the 10 MHz re-
ference oscillator, and in CW mode the carrier signal from the beat fre-
quency oscillator BFO is used.
This frequency can be varied between 599.5
kHz and 601.8 kHz.
The AGC DETECTOR AND AMPLIFIER consists of the AM AGC system and the hang
AGC system.
The audio frequency signal is fed from the detector to the AF FILTER AND
AMPLIFIER, consisting of an audio filter,
a preamplifier and an output
power amplifier, which delivers signal to the fixed AF output (0 dBm),
the headphones and the speakers.
FREQUENCY GENERATION
The necessary frequencies are generated by two frequency synthesizers accor-
ding to the phase locked principle.
Local oscillator signal fLO, to FIRST MIXER is generated in the phase locked
loop
1
and has a resolution of 1 kHz.
Local oscillator signal fL02 to SECOND MIXER is generated in the phase locked
loop 2 and has a resolution of
100
Hz, and continuous tuning over the 100 Hz
steps by means of the CLARIFIER.
LOOP
1
The voltage controlled oscillator (VCO) generates the necessary local oscilla-
tor signal to FIRST MIXER in twelve 2 MHz bands selected by the BAND CONTROL
UNIT. Inside each 2 MHz band the VCO frequency fLOl
is controlled by a DC con-
trolled voltage derived from the PHASE DETECTOR and filtered out in the LOOP 1
FILTER.
10
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